Retroperitoneal seminoma

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Retroperitoneal seminoma

Findings

Contrast-enhanced CT of the abdomen and pelvis with coronal and sagittal
reconstructions (Figures 1, 2 and 3) revealed a 7-cm homogeneous,
well-circumscribed, soft-tissue mass just caudal to the third portion of
the duodenum to the right of the midline with marked compression of the
inferior vena cava. No lymphadenopathy was identified. A diagnosis of
pure seminoma, likely metastatic, was made by on image-guided biopsy. A
testicular ultrasound was performed after to diagnosis and showed only a
small right hydrocele with no focal masses or calcifications. The mass
was surgically resected, and the patient declined an orchiectomy. After 3
cycles of platinum-based chemotherapy, the patient’s tumor markers have
normalized.

Discussion

Between 2% and 5% of malignant germ-cell tumors in men arise at
extragonadal sites. Whether these tumors develop primarily at
extragonadal sites or represent metastases of a primary testicular tumor
remains uncertain. Most extragonadal germ-cell tumors (EGCTs) are
likely metastases of a viable or burned-out testicular tumor.1
They typically arise at or near the midline presenting as brain,
mediastinal, retroperitoneal, spinal, or sacrococcygeal masses.2 Seminomas account for 30% to 40% of EGCTs, and the retroperitoneum is the second most common site after the mediastinum.3

Extragonadal
seminomas usually appear as large, lobulated, well-marginated, and
homogeneous masses on CT and magnetic resonance (MR). Although invasion
of adjacent organs is rare, metastases to regional lymph nodes and bone
can be seen. Calcifications are uncommon, and it is very rare for these
tumors to have a cystic component.4

Patients with retroperitoneal germ cell tumors usually present after their tumors have reached large dimensions.

Symptoms are nonspecific and may include a palpable abdominal mass with or without pain, backache, and weight loss.3
Beta-human chorionic gonadotropin hormone is elevated in 5% to 10% of
patients. Scrotal ultrasound and urologic exam is important since
burned-out testicular tumors have been detected in 76% of cases of EGCT.1

Survival
of patients with extragonadal seminoma is generally good with 5-year
survival rates of 90% following treatment with platinum-based
chemotherapy.5

The differential diagnosis of a
homogeneous, soft-tissue mass in the retroperitoneum includes lympho
ma, metastasis, soft-tissue sarcoma, malignant fibrous histiocytoma, and
neurogenic tumor. Diagnosis is based on biopsy with adequate tissue for
microscopic examination, flow cytometry, immunostaining, and other
molecular studies.

Conclusion

Extragonadal germ cell tumor in the retroperitoneum is rare. Although
imaging of this tumor is somewhat nonspecific, this rare entity should
be considered in the differential diagnosis of a male patient presenting
with a single, homogeneous, soft-tissue mass occurring at or near the
midline, especially if in the mediastinum or retroperitoneum.